Igniting device for internal combustion engines



June 4, 1935.

T, G. M DOUGAL IGNITING DEVICE FOR INTERNAL COMBUSTION ENGINES Filed June 50, 1953 I I gwuenkw I fikz .%a yd/ 5 MH\\\\.\ I 2 4 a a Patented June 4, 1935 lemme nnvrca non. INTERNAL counus'rron enemas Talne G. McDougal, Flint, Mlcln, assignor, mesnc assignments, to General Motors 001110! ration, Detroit, Mlcln, a corporation of Dela- Applicatlon June 30, 1933, Serial No. 678,339

g 6 Claims.

My invention relates to igniting devices for igniting the combustible mixture in internal combustion engines, the same being similar in a general way to spark plugs although certain featuresof the engine enter into the structure and opeteration of the device wherein my invention con sis s.-

The object of my invention is to provide an igniting device wherein the insulating member for the central electrode (which is equivalent to insulating members and central electrodes of ordinary spark plugs) is kept cooler than has heretofore been the case, thus lessening the tendencyof the combustible mixture to preignite and l5 reducing the liability' of the insulating member injured by the burning gases within the engine cylinder. This keeping of the insulating member (which is ordinarily made of ceramic material) as cool as possible is becoming of progresslvely more importance as compression pressures before ignition are increased, with resulting higher, temperatures of the mixture after the ignition thereon-and that end is attained by the invention herein by providing for a more direct and unrestrained flow of heat from the insulating member and especially from the lower end thereof, into the mass of cooling medium within the cylinder'head, all as will hereinafter appear in describing my invention and explaining the operation thereof.

. The drawing submitted herewith illustrates three ways differing slightly each from the others "whereby my invention may be carried out, and theobiect thereof attained, and the concluding claims particularly point out the features wherein my invention consists.

In the drawing accompanying and forming a part of this application: I t

Figure 1 is a view showing a longitudinal section upon a centralplane of my improved spark plug and its relation to the head of the engine with which it is used, the insulating member of theplug, however, being shown in side elevation. 4 Figure 2 is a view showing the same upon a transverse plane indicated by the line 2-2,-Flgure 1. 4

Figure 3 isa sectional view similar to Figure 1 showing a modified form of my improved spark plug. Figure 4 is a similar sectional view showing still another form of my invention.

Referring now to the drawing, the numerals designate the head of an internal combustion engine having'the usual cooling medium" 5 space 6 for limiting the rise of temperature in the head, the upper and lower walls of the head being connected by an annular partition or wall 'I which provides a chamber 8 having an enlarged upper part open at its upper end, and within which the external shell 9 of my improved spark 5 plug is housed; said shell. being threaded as shown to engage internal threads in the enlarged upper part of the chamber so that the shell may be conveniently put in place and removed therefrom. I The-lower part III of the chamber 8 com- 10 municates with the interiorof the engine cylinder and is smaller than the upper internally threadas shown for securing liquid tight joints be-" tween the lower end of the shell and the ledge,"

and between the usual hexagonal upper part l4 of'the shell and the upper wall of the cyl. inder head. The shell 9 being in intimate contact with theinterior of the chamber within which it is housed, a substantially continuous metallic path is provided through which such heatas may reach the shell is conducted to the cooling liquid within the space 5, whereby the shell is kept cool when the engine is in operation.

The insulating member I5 may be secured within the shell 9 in any way as by an inturned holding flange l6, and the same is spaced from the interior of the shell 9 so as to provide an annular cooling jacket I'l surrounding the insulator. When the shell is in place within the chamber 8 this cooling jacket is in direct communication with the interior of the head through registering holes l8, IS in the wall! and shell 9, so that the cooling medium within head space 6 enters the cooling jacket I! to thereby cool the insulatin member- The lower end of the insulating member Ii enters the smaller lower part II of the chamber 8; and the same is preferably made conical, as 45 shown. This conical lower end being located in close proximity to the conical inner surface of the comparatively small conical chamber, and the surfaces of said lower end and the interior of the chamber being approximately parallel.

. it follows that a considerable part of the heat imparted by the combustion gases to the insulat-' ing member will be radiated from said lower end to the relatively cooler wall of said chamber, and will il'o'w rapidly therethrough and to the insulating member are to a considerable degree independent of one another, and a plug in which both are present will be kept cooler than has been the case in spark plugs such as have heretofore been in use.

The insulating member l5 has the usual insulated electrode extending through it; and the grounded electrode 2| preferably extends into the cooling liquid space 6 in the head, as shown, to thereby the more efiectively cool the same.

In the form of my invention illustrated in Figure 3 the grounded electrode 22 is carried by the shell 23 so that the plug is a single self-contained device in which particular it more closely resem bles spark plugs as ordinarily made. The shell 23 has threaded engagement at 24 with the inner of the spaced walls of the cylinder head, and the wall I of the Figure 1 form is omitted; so that there are no chambers separate and distinct from the plug shell itself housing the shell and the lower end of' the insulating member 25. This permits the cooling liquid in the space-26 to come into direct contact with the shell 23 (which does not occur in the form shown in Figure 1) so that in this form the shell itself is more eifectively cooled than in the Figure 1 form. However and in this second form the cooling liquid within the space 26enters a jacket 21' through holes 23 and comes into direct contact with the insulating member so that it is cooled to the same degree,

r and in the same way as in the form of my invention first described. Heat from the lower end of the insulating member is, however, radiated and flows to the cooling liquid within the space 25 through the lower end of the shell 23 in substantially the same way as in the form shown in Figure 1; and in both forms there is a transfer of heat 'from the insulating member to the cooling liquid within the head through separate paths one directly to the cooling liquid in the head space 5, and the other through the liquid within the jacket 21 and to thesame mass of cooling liquid within the head.

In the form of my invention illustrated in Figure 4 a wall 29 like the wall I in Figure 1 provides an upper. internally threaded chamber into which the spark plug shell 30 screws, and a lower and smaller conical chamber 3| into which the lower end cf the insulating member 32 extends; there being a ledge 33 between the chambers as in the form illustratedin Figure 1. In this form the cooling liquid within the space 34 of the head does not come into direct contact with the insulating member-as in the forms of my invention illustrated in Figures 1 and 3, but the shell 30 is cooled in substantially the same way and to the same extent asimthe Figure 1 form; and the arrangemerit of the lower end of the insulating member within, and with its peripheral surface adjacent the interior of the lower chamber 3|, secures a plug wherein a large part of the heat communicated to the insulating member is radiated and flows with a minimum of restraint directly into the cooling liquid within the head space 34; while such heat as flows upward along the member and heats the shell 30 flows without substantial restraint through the upper threaded surfaces of the shell 30 and the wall 23 and into the cooling liquid in the space 34. The grounded electrode 35 in this form of-my invention is shown as within a passage in the inclined wall of the lower chamber 3| instead of extending into the cooling liquid space 34, but it will nevertheless be efiectively cooled because of its long and intimate contact with said wall which is a good conductor of heat and its location close to the cooling liquid within the head space 34.

The series of holes I! in the wall I and IS in the shell 9 are made quite numerous as shown, and one series preferably has an odd'and' the other an even number of holes; the purpose of this being to insure registry of a plurality of pairs of holes, and free access of cooling medium to the cooling jacket l1, whatever angular position the shell may come to rest in as it is screwed into the chamber 3.

Having thus described and explained my invention I claim and desire to secure by Letters Patent:

. 1. In an igniting device of the class described and in combination with a cylinder head having spaced walls whereby a cooling medium space is formed; a hollow shell arranged to be cooled by a cooling medium within said cooling liquid space; an insulating member secured within and spaced apart from the interior of said hollow shell to thereby provide a cooling liquid jacket between the two, said hollow shell having a hole whereby said jacket is placed in communication with the cooling liquid space within said head; an insulated electrode carried by said insulating member; and a grounded electrode arranged in sparking relation with the inner end of said insulated electrode.

2. In an igniting device of the class described and in combination with a cylinder head having spaced walls whereby a cooling liquid space is formed; an annular partition connecting said walls and so shaped as to provide a large upper ;chamberopen at its upper end, and a lower chamber smaller than the upper chamber and communicating at its lower end with the interior of the cylinder; a hollow shell secured within said upper chamber; an insulating member secured which insulating member extends into the smaller lower chamber aforesaid; registering holes in said annular partition andin said-shell whereby said jacket is placed in communication with the cooling liquid space within said head; an insulated electrode carried by said insulating member; and a groundedelectrode arranged insparking relation with the inner end of said insulated electrode. 3. In an igniting device of the class described and in combination with a cylinder head having spaced walls whereby a cooling liquid space is formed; an annular partition connecting said walls and so shaped as to provide a large upper chamber open at its upper end, an intermediate ledge, and a lower chamber belowsaid ledge and smaller than said upper chamber, and which vide a cooling liquid jacket between the two, and

the lower end of which insulating member extends into the smaller lower chamber aforesaid; registering holes in said annular partition and in said shell whereby said jacket is placed in communication with the cooling liquid space within said head; an insulated electrode carried by said insulating member; and a grounded electrode arranged in sparking relation with the inner end of said insulated electrode.

4. In an igniting device of the class described and in combination with a cylinder head having spaced walls whereby a cooling liquid space is formed; a hollow shell arranged to be cooled by cooling liquid within said cooling liquid space;

' an insulating member secured within said hollow shell; an insulated electrode carried by said insulating member; and a grounded electrode arranged in sparking relation with the inner end of said insulatedelectrode and extending through the lower of said head walls and into the cooling liquid space within said head.

5'. In an igniting device of the class described and in combination with a cylinder head having spaced walls whereby a cooling liquid space is formed; an annular partition connecting said walls and so shaped as to provide a large upper chamber open at its upper end, and a lower chamber smaller than the upper chamber and communicating at its lower end with the interior oi. the cylinder; a hollow shell, secured within said upper chamber; an insulating member secured within said hollow shell, and the lower end of which insulating member extends into the smaller lower chamber aforesaid; an insulated electrode carried by said insulating member; and a grounded electrode arranged in sparking relation with the inner end of said insulated electrode and extending through the lower'of said head walls and into the cooling'liquid space within said head.

6. In an igniting device of the class described and in combination with a cylinder head having spaced walls whereby a cooling medium space is formed; a hollow shell arranged to be cooled by a cooling medium within said cooling liquid space; an insulating member secured within and spaced apart from the interior of said hollow shell to thereby provide a cooling liquid jacket between the two; means for supplying a cooling liquid to said jacket, to thereby cool said insulating member by direct contact of a cooling liquid therewith; an insulated electrode carried by said insulating member; and a grounded electrode arranged in sparking relation with the inner end oi. said insulated electrode.

TAINE G. McDOUGAL. 

